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1、 NEMA OS 3 NEMA OS 3 SELECTION AND INSTALLATION GUIDELINES FOR ELECTRICAL OUTLET BOXES Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 04:04:08 MDTNo reproduction or networking permitted without l
2、icense from IHS -,-,- Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 04:04:08 MDTNo reproduction or networking permitted without license from IHS -,-,- NEMA Standards Publication OS 3-2007 Select
3、ion and Installation Guidelines for Electrical Outlet Boxes Published by: National Electrical Manufacturers Association 1300 North 17th Street, Suite 1752 Rosslyn, Virginia 22209 www.nema.org Copyright 2007 by the National Electrical Manufacturers Association. All rights, including translation into
4、other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions. Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALic
5、ensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 04:04:08 MDTNo reproduction or networking permitted without license from IHS -,-,- NOTICE AND DISCLAIMER The information in this publication was considered technically sound by the consensus of persons engaged in the development and approval of t
6、he document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document. The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document c
7、ontained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or seeks out the views of persons who have an interest in the topic covered by this publication. While NEMA administers the process and establishes rules to
8、promote fairness in the development of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability f
9、or any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, express
10、or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any of your particular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufacturer or
11、sellers products or services by virtue of this standard or guide. In publishing and making this document available, NEMA is not undertaking to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to s
12、omeone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this publicati
13、on may be available from other sources, which the user may wish to consult for additional views or information not covered by this publication. NEMA has no power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect product
14、s, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safetyrelated information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. Copyright Nation
15、al Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 04:04:08 MDTNo reproduction or networking permitted without license from IHS -,-,- NEMA OS 3-2007 Page i CONTENTS Foreword .iii Introductioniv Section 1 PRODUCT SEL
16、ECTION.1 1.1 The Outlet Box for the Type of Wiring System Used 4 1.1.1 Connection to the Wiring System4 1.1.2 Wiring Systems Employing Tubing or Conduit .4 1.1.3 Wiring Systems Employing Metal Jacketed or Nonmetallic-Sheathed Cable 4 1.1.4 Grounding5 1.2 Select the Box Based on Contents and Function
17、 after Installation.5 1.2.1 Internal Volume Capacity of Boxes.5 1.2.2 Junction and Pull Boxes6 1.2.3 Outlet and Device Boxes Mounting of Wiring Devices 6 1.2.4 Outlet and Device Boxes Support of Fixtures/Luminaires, Ceiling Suspended Fans, and Other Products.7 1.2.5 Outlet and Device Boxes with Fire
18、 Resistance Ratings (hours).8 1.2.6 Boxes for High and Low Voltage Wiring Circuits (Class 1, Class 2, and Class 3 Circuits) .8 1.3 Select the Outlet Box for the Intended Location of Installation .9 1.3.1 General9 1.3.2 Boxes for Installation in or on Walls or Ceilings10 1.3.3 Boxes for Installation
19、in Floors11 1.3.4 Boxes for Other Locations.12 1.3.5 Outlet and Device Boxes for use in Fire Resistance-Rated Construction14 1.3.6 Special Use Boxes15 1.3.7 Covers and Cover Plates for Dry Locations15 1.3.8 Extension Rings and Box Extenders.16 Section 2 PRODUCT INSTALLATION .22 2.1 Introduction22 2.
20、1.1 Storage and Preparation for Installation .22 2.1.2 Coordinating Trades (after Boxes are Mounted) 22 2.2 Fire Resistance-Rated Construction .22 2.2.1 Metallic Boxes.23 2.2.2 Nonmetallic Boxes 24 2.3 Mounting and Securing of Electrical Boxes.25 2.3.1 General25 2.3.2 Surface Mounting on Walls or Ce
21、ilings.25 2.3.3 Boxes Supported by Raceways25 2.3.4 Flush Mounting in Walls and Ceilings.25 2.3.5 Pendant Mounting.26 2.3.6 Pedestal Mounting 27 2.3.7 Masonry Wall Mounting.27 2.3.8 Floor Box Mounting.27 2.3.9 Poke-through Floor Fitting-Mounting 28 2.3.10 Other Boxes 28 2.4 Connection to Wiring Syst
22、ems 29 2.4.1 General29 2.4.2 Connection to Conduit Entries 29 2.4.3 Connection to Cable Entries .31 2.4.4 Connection to High and Low Voltage Wiring Circuits.33 2.5 Completing the Installation33 2.5.1 Introduction33 2.5.2 Grounding and Bonding33 Copyright 2007 by the National Electrical Manufacturers
23、 Association. Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 04:04:08 MDTNo reproduction or networking permitted without license from IHS -,-,- NEMA OS 3-2007 Page ii 2.5.3 Installation of Wiring
24、 Devices35 2.5.4 Flush-Device Boxes: Coordination with Finished Wall Surface Installation .37 2.5.5 Installation of the Cover and/or Cover Plate.38 2.6 Verfication of Installation .38 Tables 1-1 Summary Table for Support of Luminaires/Fixtures and Other Products.8 2-1 Recommended Set Times for Cemen
25、ted Joints .31 Figures 1-1 Typical Box Mounting Positions 17 1-2 Typical Box Mounting Styles .19 1-3 Separately Supplied Box Supports20 2-1 Square Boxes In 4” X 4” Wall Opening .24 2-2 Typical Threaded Conduit Entries.30 Copyright 2007 by the National Electrical Manufacturers Association. Copyright
26、National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 04:04:08 MDTNo reproduction or networking permitted without license from IHS -,-,- NEMA OS 3-2007 Page iii Foreword User input has been considered in the deve
27、lopment of this Standards Publication. The Standards Publication was developed by the NEMA Outlet and Switch Box Section, which periodically reviews it for any revisions necessary to address changing conditions, product listing and installation requirements, and technical progress. Comments for prop
28、osed revisions are welcomed and should be submitted to: Vice President, Technical Services National Electrical Manufacturers Association 1300 North 17th Street, Suite 1752 Rosslyn, VA 22209 Copyright 2007 by the National Electrical Manufacturers Association. Copyright National Electrical Manufacture
29、rs Association Provided by IHS under license with NEMALicensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 04:04:08 MDTNo reproduction or networking permitted without license from IHS -,-,- NEMA OS 3-2007 Page iv Introduction There may be no other component of our electrical distribution system
30、that serves more purposes than the electrical outlet box. When installed with a cover, the box 1. provides connection to a raceway system and a means to access wiring; 2. houses and provides a degree of mechanical protection for conductor splices, and wiring devices such as switches and receptacles;
31、 and 3. limits access to live parts; and where applicable, bonds electrically conductive components to the equipment grounding conductor. When designed and specifically identified for the purpose, a box and other components form an enclosure system which 1. provides degrees of protection from extern
32、al environmental conditions (rain, dust, scrub water, etc); 2. preserves the integrity of fire resistance rated walls, ceilings, floors, partitions, or furniture in which it is installed; and/or 3. provides independent support for attached fixtures such as luminaires, ceiling suspended fans, and saf
33、ety and security devices. For the most part, boxes within the scope of these guidelines fall into just a few general classifications. Each classification has been adapted over the years to meet market needs. These guidelines are written by the NEMA Outlet and Switch Box Section (5-OS) to provide qua
34、lified designers, installers, and inspectors with an industry perspective of the appropriate selection and installation criteria based on the designed, intended use of the product. The member companies of the NEMA 5-OS Section promote selection and installation of listed boxes and covers, and listed
35、 raceways and fittings. Listing of electrical system components qualifies them to minimum performance requirements and provides for ongoing conformity surveillance. Listed boxes and covers can be recognized by the trademark of the qualified electrical testing laboratory on the part or its smallest u
36、nit container. It is our objective to develop a closer liaison with the installers of our products and the professional electrical inspector. Through this liaison, we intend to provide uniform education and understanding as to the intended use and application of our products. Through education, we h
37、ope to develop an alliance, founded in trust that will ensure that the concerns and challenges we each face are addressed. Compatibility of Boxes with Metallic and Nonmetallic Wiring SystemsGrounding and Bonding Metal and nonmetallic outlet boxes are typically designed for use in electrical distribu
38、tion systems rated 600 volts or less. Metal systems and raceways that are recognized as equipment grounding conductors provide protection by grounding and bonding the entire system. All the components of the system (boxes, fittings, devices, fixtures, raceways, etc.) with proper installation are des
39、igned to maintain continuous grounding and bonding throughout the system. Products must be installed so that the removal of any device, fixture or box cover does not interrupt the downstream grounding or bonding path. Nonmetallic systems protect the installer and end users by providing isolation (in
40、sulation) throughout the wiring system. All the components (boxes, fittings, devices, fixtures, raceways, etc.) with proper installation are designed to maintain this isolation (insulation). When properly installed: Copyright 2007 by the National Electrical Manufacturers Association. Copyright Natio
41、nal Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=Boeing Co/5910770001 Not for Resale, 07/25/2008 04:04:08 MDTNo reproduction or networking permitted without license from IHS -,-,- NEMA OS 3-2007 Page v a) there are no ungrounded exposed metal parts that may be
42、 likely to become energized in case of a ground fault; b) ground wires are installed inside the raceways and throughout the system; and c) ground wires are joined so that removal of a device or fixture does not interrupt the downstream ground path. Generally, this is done by joining the incoming and
43、 outgoing ground wires with a third ground wire that then attaches to the device or fixture. Thus, the removal of the device or fixture does not affect the downstream ground path. Each system is designed to distribute electrical power while protecting the installer and end users. Metallic and nonmet
44、allic systems employ different means to provide protection. Therefore, for safety reasons, these two systems should not be randomly mixed without due consideration. Where it is necessary and desirable to mix metallic and nonmetallic components in a wiring system, special products, applications and p
45、rocedures can be used to ensure the desired level of safety in accordance with the National Electrical Code. Product Standards and Installation Codes Boxes and covers within the scope of these guidelines are designed for installation in compliance with the National Electrical Code (NEC) NFPA 70. The
46、 broadest range of general purpose designs are included in ANSI/NEMA OS 1, Sheet-Steel Outlet Boxes, Device Boxes, Covers, and Box Supports; and ANSI/NEMA OS 2, Nonmetallic Outlet Boxes, Device Boxes, Covers and Box Supports. NEMA FB 1, Fittings, Cast Metal Boxes, and Conduit Bodies for Conduit, Tub
47、ing, and Cable Assemblies, contains those boxes described in its title, and ANSI/NEMA WD 6, Wiring DevicesDimensional Requirements, includes flush-device cover plates. Conformity to these standards provides assurance of the compatibility and interchangeability of box designs with covers, raceways, w
48、iring devices and other components of the electrical distribution system whose performance may be dependent on the box design. Listed boxes are typically evaluated to the safety and performance requirements of ANSI/UL 514A, Metallic Outlet Boxes or ANSI/UL 514C, Nonmetallic Outlet Boxes, Flush-Device Boxes, and Covers. The safety and performance requirements for flush-device cover plates are covered in ANSI/UL 514D, Covers for Flush-Mounted Wiring Devices. Boxes intended to provide degrees of protection f